linux-kernel - [PATCH v4 2/2] Revert "drm/vblank: Do not update vblank count if interrupts are already disabled."

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 28 Jun 2019 13:05:32 +0100
From:   Robert Beckett <bob.beckett@...labora.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Robert Beckett <bob.beckett@...labora.com>
Subject: [PATCH v4 2/2] Revert "drm/vblank: Do not update vblank count if interrupts are already disabled."

If interrupts are already disabled, then the timestamp for the vblank
does not get updated, causing a stale timestamp to be reported to
userland while disabling crtcs.

This reverts commit 68036b08b91bc491ccc308f902616a570a49227c.

Signed-off-by: Robert Beckett <bob.beckett@...labora.com>
---
 drivers/gpu/drm/drm_vblank.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 7dabb2bdb733..aeb9734d7799 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -371,25 +371,23 @@ void drm_vblank_disable_and_save(struct drm_device *dev, unsigned int pipe)
 	spin_lock_irqsave(&dev->vblank_time_lock, irqflags);
 
 	/*
-	 * Update vblank count and disable vblank interrupts only if the
-	 * interrupts were enabled. This avoids calling the ->disable_vblank()
-	 * operation in atomic context with the hardware potentially runtime
-	 * suspended.
+	 * Only disable vblank interrupts if they're enabled. This avoids
+	 * calling the ->disable_vblank() operation in atomic context with the
+	 * hardware potentially runtime suspended.
 	 */
-	if (!vblank->enabled)
-		goto out;
+	if (vblank->enabled) {
+		__disable_vblank(dev, pipe);
+		vblank->enabled = false;
+	}
 
 	/*
-	 * Update the count and timestamp to maintain the
+	 * Always update the count and timestamp to maintain the
 	 * appearance that the counter has been ticking all along until
 	 * this time. This makes the count account for the entire time
 	 * between drm_crtc_vblank_on() and drm_crtc_vblank_off().
 	 */
 	drm_update_vblank_count(dev, pipe, false);
-	__disable_vblank(dev, pipe);
-	vblank->enabled = false;
 
-out:
 	spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
 }
 
-- 
2.18.0